The aquation of hexachlorotechnetate(IV)

The Present Status of Technetium Chemistry

“…4) was detected and discussed. K 2 [TcCl 6 ] shows a transition from the paramagnetic to the antiferromagnetic state at the Néel temperature of 7.0 Κ [115], The photochemical decomposition of (NH 4 ) 2 [TCC1 6 ] in acidic aqueous solutions [116] and the thermal stability of (NH 4 ) 2 [Tcl 6 ] and K 2 [Tcl 6 ] [ 117] have been studied. Investigations on the electrochemical reduction of [TcCl 6 ] 2 ~ and [TcBr 6 ] 2 ~ were carried out with solutions of the tetrabutylammonium salts in acetonitrile [118].…”

A Novel Approach to the Oxidation Potential of the Tc(VII)/Tc(IV) Couple in Hydrochloric Acid Medium through the Reduction of TCO- 4 by Fe2+ Ion

“…The positive charge of Tc(IV) species obtained from aquation of TcCl|~ in 1.0 M HCl has been reported by several authors [9,21]. The solubility of Tc0 2(so ii d) as a function of pH by Meyer et al [5] suggests that one deals with Tc0 2+ ions.…”

“…1) in 1.0 M HCl leads to a Tc(IV) solution, with concentration higher than the 5.4X10" 5 M saturated solution obtained by Meyer et al [5] by dissolution of electrodeposited Tc0 2 . Other investigators [9] prepared Tc(IV) 0.006 M in 1.0 M HCl solutions by diluting the TcCl|" ions obtained in concentrated HCl. It seems that the inertia of the Tc(IV) complexes leads to different results depending on the starting complexe.…”

“…Three formal potentials were calculated using equation (9): i) Ε'°, which implies that Tc(IV) (aq) is present in the solution as TcO(OH) 2 or Tc(0H) 4 , is used for sake of comparison, as the solubility measurements of Tc0 2 . 1.63 H 2 0 [5] and the hydrolysis constants of Tc0 2+ [16] do not sustain the presence of pure soluble TcO(OH) 2 at the low pH used here, ii) which supposes that one deals with Tc(IV) (aq) as TcO + ions complexed by chlorides and iii) Eá 0 , associated to chloride complexes of Tc 4+ .…”

“…A ultraviolet visible Shimadzu 2101PC spectrophotometer was used to determine ferric iron concentration (λ = 336 nm, ε = 200 m 2 mol" 1 in 1.0 M HCl) in solution so as to estimate diluting effect, to follow the disappearance of Tc(Vn) {λ = 244 nm, ε = 622 m 2 mol" 1 and λ -287 nm, ε = 236 m 2 mol" 1 [8]) and the appearance of Tc(IV) (λ = 240 nm and λ -338 nm, ε = 1104 -3200 m 2 mol" 1 [9,10]) when the concentration of technetium enabled it. Titration of Fe(II) ions through redox reaction with cerium Ce(IV) (1.28 V for Ec°e(iv)/cc(nT) in 1.0 M HCl) was performed using a voltmeter fitted with Pt and Ag/AgCl electrodes.…”